1. Field of the Invention
The present invention relates to a ratchet wrench, and more particularly to a reversible ratchet wrench capable of switching its rotational direction.
2. Background of the Invention
A conventional ratchet unit for a reversible ratchet wrench is disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 10-217140.
The ratchet unit is accommodated within the head of the ratchet wrench and has a drive shaft and a ratchet direction selector. The ratchet direction selector is operated by an operator in order to rotate a socket attached to the drive shaft clockwise or counterclockwise about the drive shaft. The drive shaft extends outward from the head in a transverse direction and releasably holds the socket in such a manner that the socket rotates together with the drive shaft in order to fasten or loosen a fastening member such as a nut or bolt.
However, the conventional ratchet direction selector is disposed on the head at the back of the drive shaft, and therefore is located at a position remote from a hand which grips the handle of the ratchet wrench so as to hold the ratchet wrench.
Therefore, when the operator wishes to change the rotational direction of the socket between the clockwise and counterclockwise directions, the operator must rotate the knob of the ratchet direction selector with his other hand (i.e., the hand that does not grip the handle of the ratchet wrench). In other words, the operator must use both hands in order to change the rotational direction of the socket.
In the case in which an operator wishes to loosen a nut or bolt which the operator has fastened, or to fasten a nut or bolt which the operator has loosened, within a narrow space into which the operator can barely insert the ratchet wrench, the operator must remove the ratchet wrench from the space, and then rotate the knob of the ratchet direction selector with both the hands in order to switch the rotational direction of the socket. This deteriorates work efficiency.
In consideration of the above-described problem of the conventional art, an object of the present invention is to provide a ratchet wrench which enables a user to switch rotational direction of a socket by sole use of one hand which grips the handle of the ratchet wrench.
In order to achieve the above object, the present invention provides a ratchet wrench in which rotation of an output shaft of an air motor is transmitted to a ratchet unit via a reduction gear unit in order to rotate a spindle connected to the ratchet unit, the ratchet unit being accommodated within a ratchet housing, the ratchet wrench comprising a cover plate covering one face of the ratchet housing opposite the other face thereof from which the spindle projects; a pair of reverse buttons disposed on the cover plate to be slidable along a direction parallel to the output shaft of the air motor; a pair of reverse arms rotatably attached to the reverse buttons, each reverse arm being movable together with the corresponding reverse button; and a reverse gear which the reverse arms engage upon movement of the reverse arms caused by sliding movement of the reverse buttons, the reverse gear being rotated in one direction when one of the reverse arms engages the reverse gear and rotated in the opposite direction when the other reverse arm engages the reverse gear.
Preferably, the reverse arms are coupled with first ends of a pair of springs, whose second ends are fixed to the cover plate, the springs urging the reverse arms toward a direction away from the reverse gear; and the reverse arms each have a curved portion which abuts a toll pin fixed to the cover plate.
Preferably, a spring is provided between and connected to the pair of reverse arms in order to urge them to approach each other.
Preferably, each of the reverse arms has a rack at an end portion that engages the reverse gear.
Preferably, the rack is formed in such a manner that the pitch line of the rack inclines with respect to the longitudinal axis of the corresponding reverse arm.
The above-described structure enables a user to switch rotational direction of the spindle through simple operation of sliding the pair of reverse buttons by use of the thumb of a hand which grips the handle of the ratchet wrench. Therefore, the easiness of operation of the ratchet wrench can be improved greatly.